Tim, all I can think of is Corian, and I don't even know if that is plastic, but it would be heavier than the wood.
Now I wonder if the ABS plastic panels, which can come in very thin sizes could work? Bill was teaching us about using these for oils, but I am going to let Carl tell you about them. Too much of a guy thing for me. I would think you know about them, but others might not.
Side note: Carl you look much cuter than your palette!
